In butterfly valves such as are used in controlling the flow of liquids to heating systems as in autmobile heating systems, it is common to provide a body having a generally cylindrical passage, a pivot pin extending radially into the passage and a valve plate fixed to the pin so that when the pin is rotated, the plate is moved into open or closing relationship to the periphery of the passage.
A common problem with respect to such valves is that due to the tolerances in manufacture of the parts, it is difficult to obtain a seal between the valve plate and the inner surface of the passage. In an effort to facilitate obtaining the seal, the plate usually has a periheral portion made of resilient material. However, even in such an instance, the pin usually engages a diametral groove in the plate and if the tolerances are beyond permissible limits, it is quite common to encounter leakage along at least a portion of the periphery of the valve when the valve is in closed position.
Accordingly among the objects of the invention are to provide a butterfly valve which will minimize the problem of leakage. A further object of the invention is to provide a method of making a valve which obviates the problem of leakage.